Mattress

ABSTRACT

A mattress including a mattress core (1) having a plurality of elastically compressible core elements (5, 6) of which at least some are adjustable in respect of the hardness thereof. The core elements (6), which are adjustable in respect of the hardness thereof, have an upper support part (7) having an upper support surface (8), a lower support part (9) having a lower support surface (10) and at least one pretensioned spring (23, 24), by the pretension force of which the upper and the lower support parts (7, 9) are held at a distance from one another. The pretension force of the springs (23, 24) is adjustable.

TECHNICAL FIELD

The invention relates to a mattress with a mattress core which has aplurality of elastically compressible core elements, of which at leastsome are adjustable in their hardness.

BACKGROUND

Various designs of mattresses are known. For example, spring coremattresses have with a mattress core which has a multiplicity of helicalsprings. There are cushioning layers, in particular made of foam, aboveand below the spring core. A mattress cover forms the outer enclosure ofthe mattress.

In order to satisfy different users' requirements, mattresses ofdifferent strength or hardness are provided. Approaches also alreadyexist to form the hardness of a mattress in an adaptable manner.

US 2003/009830 A1 presents a mattress having a plurality of foamelements assigned to different body regions, wherein the hardness of afoam element can be changed by letting air into, or extracting air from,an enclosure surrounding the foam element in an air-tight manner. Amongthe disadvantages here is the fact that the height of the settableelements depends on the set hardness. If zones of different hardness areintended to be set, this leads to different heights of the foamelements. In addition, moisture accumulates on an air-impermeable layer.

US 2010/064443 A1 discloses a mattress with a plurality of transverselylying, air-filled tube elements, wherein the air pressure of theelements can be changed by a pump or electrically activatable valve inorder to set the hardness of the mattress. However, the spring comfortof inflated tube elements is limited, and there is the risk of anaccumulation of moisture.

U.S. Pat. No. 4,190,914 discloses a mattress which does not have anydifferent zones, i.e. does not have a mattress core which has aplurality of elastically compressible core elements, of which at leastsome are adjustable in their hardness. The mattress shown there isadjustable overall in its hardness, wherein a plurality of springs arearranged on a lower support part, said springs being supported at theirupper end on an elastic element, in particular a mesh wire, wherein thelower support part is designed to be raiseable and lowerable in order tovary the pretensioning of the springs.

SUMMARY

It is the object of the invention to provide an advantageous mattress ofthe type mentioned at the beginning, the hardness of which is adjustablein a simple manner and which can be formed with a high degree ofstability. This is achieved by a mattress with one or more featuresdisclosed below.

The mattress according to the invention has a mattress core with coreelements which are adjustable in their hardness and each have an uppersupport part with an upper support surface and a lower support part witha lower support surface. In addition, the adjustable core elements eachhave at least one pretensioned spring, by the pretensioning force ofwhich the upper and the lower support parts are held at a mutualdistance. In order to adjust the hardness of the mattress in the regionof the respective adjustable core element, the pretensioning force ofthe at least one spring of the respective adjustable core element isadjustable.

Simple mechanical adjustability of core elements of the mattress canthereby be made possible. In addition, advantageous spring properties ofthe core elements can be provided and the mattress can have a highdegree of stability over the long term.

A cushioning layer which comprises an elastic material, for example afoam material and/or latex material, is advantageously provided abovethe upper support surface. This cushioning layer can be formed in aconventional manner.

In an analogous manner, a cushioning layer which comprises an elasticmaterial, for example a foam and/or latex, is advantageously providedbelow the lower support surface. This cushioning layer can be formed ina conventional manner. The mattress can therefore also be used in aturned-over arrangement (such that the upper support part is located atthe bottom and the lower support part is located at the top). The upperand lower cushioning layers can be formed with different properties, forexample, in order to provide a summer side and a winter side of themattress.

In an advantageous embodiment of the invention, there is at least oneoblique rod- or plate-shaped connecting part which, at its upper end, ismounted pivotably on the upper support part and, at its lower end, issupported on a supporting surface, on which the lower end is mounteddisplaceably in a sliding or rolling manner, or which, at its lower end,is mounted pivotably on the lower support part and, at its upper end, issupported on a supporting surface, along which the upper end is mounteddisplaceably in a sliding or rolling manner. The spring acts on theconnecting part or on a part connected thereto. If the upper supportpart is compressed in the direction of the lower support part, theconnecting part is pivoted in relation to the support part on which itis pivotably mounted, for example in relation to the upper support part,with the inclination of said connecting part being increased, whereinthat end of the connecting part which is remote from the pivot axis, forexample the lower end, slides or rolls along the supporting surface.This pivoting of the connecting part takes place counter to the force ofthe spring pretensioning the connecting part.

In the unloaded state of the mattress, the connecting part isadvantageously pulled by the spring against a stop (which thereforedelimits the supporting surface). The minimum inclination of theconnecting part and therefore the maximum distance between the uppersupport part and the lower support part are thereby limited. Otherdevices for limiting the maximum distance between the upper support partand the lower support part can be provided, for example cords runningbetween the upper support part and the lower support part.

There can be a motorized adjustment element, for example an electricmotor or an electric cylinder, for adjusting the pretensioning of thespring. For example, the electric motor can drive a cable drum, by whicha traction cable connected to one end of the spring can be wound up to agreater or lesser extent. Tensioning of the spring to a greater orlesser extent, in particular via a traction cable, can also take placeby a helical gearing driven by the electric motor or directly with theelectric cylinder which has already been mentioned.

Instead, there could also be a manually actuable adjustment element inorder to adjust the pretensioning of the spring. A threaded spindle, towhich a traction cable acting on the spring is attached, could berotated by a handwheel or a hand crank in order to bring about an axialadjustment in relation to a spindle nut.

The core elements which are adjustable in their hardness preferably runin the transverse direction of the mattress, particularly preferablyover at least substantially the entire width of the mattress (optionallyapart from a projecting region of the cushioning and of the mattresscover). These core elements could therefore also be referred to as “beamelements”. There are a plurality of such core elements in thelongitudinal direction of the mattress.

In addition to core elements which are adjustable in their hardness, themattress core can also have non-adjustable elastically compressible coreelements. The latter can be arranged at locations which are lesscritical for comfort when sleeping, for example in the region of thehead end and/or foot end of the mattress. There can also benon-adjustable core elements between adjustable core elements.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details of the invention will be explained belowwith reference to the attached drawing, in which:

FIG. 1 shows a schematic longitudinal section through an exemplaryembodiment of a mattress according to the invention;

FIG. 2 shows a top view of the mattress core;

FIG. 3 shows a view of an adjustable core element (viewing direction Ain FIG. 2);

FIG. 4 shows a side view of the electric adjustment motor with the cabledrum;

FIG. 5 shows an adjustable core element according to a second embodimentof the invention in an illustration analogous to FIG. 3;

FIG. 6 shows an adjustable core element according to a third embodimentof the invention in an illustration analogous to FIG. 3;

FIG. 7 shows an adjustable core element according to a fourth embodimentof the invention in an illustration analogous to FIG. 3;

FIG. 8 shows an adjustable core element according to a fifth embodimentof the invention in an illustration analogous to FIG. 3;

FIG. 9 shows a side view of the lower portions of the connecting partswith the traction cable;

FIG. 10 shows an adjustable core element according to a sixth embodimentof the invention in an illustration analogous to FIG. 3.

DETAILED DESCRIPTION

FIG. 1 shows a schematic diagram of a mattress according to theinvention in longitudinal section. The section therefore runs parallelto the viewing direction A shown in FIG. 2. However, the core elements5, 6 are merely illustrated schematically in FIG. 1 in the form ofrectangles (in the manner of black boxes).

The mattress has a mattress core 1 which is formed by the core elements5, 6. A continuous upper cushioning layer 2 is situated above the coreelements 5, 6 and a continuous lower cushioning layer 3 is situatedbelow the core elements 5, 6.

The mattress core 1 and the cushioning layer 2, 3 are enclosed by amattress cover 4 which forms the outer side of the mattress.

When, within the scope of this document, “top” and “bottom” arementioned, this relates to a possible use position of the mattress,specifically in particular to the use position illustrated in thefigures. However, in the exemplary embodiment, the mattress may also beused in the turned-around use position, in which case “top” and “bottom”are swapped.

FIG. 2 illustrates the mattress core 1 in top view. It is apparent thatthe core elements 5, 6 which form the mattress core 1 all extend overthe entire width of the mattress core 1. However, a plurality or all ofthe core elements 5 and/or 6 could extend only over part of the width ofthe mattress, and therefore two or more core elements 5 and/or 6 arearranged next to one another with respect to the width of the mattress.

In the exemplary embodiment, the mattress core 1 has core elements 5,the hardness of which is not adjustable, and core elements 6, thehardness of which is adjustable. However, there could also only beadjustable core elements 6.

The design of the adjustable core elements 6 is revealed more preciselyin FIGS. 3 and 4. The adjustable core elements 6 each have an inherentlyrigid upper support part 7 with an upper support surface 8, and aninherently rigid lower support part 9 with a lower support surface 10.The support surfaces 8, 10 which are directed away from each other areformed flat and have rectangular shapes which are congruent, as seen intop view.

The upper support surfaces 8 of the upper support parts 7 of all of thecore elements 5, 6 of the mattress core 1 lie in a common plane.Similarly, the lower support surfaces 10 of the lower support parts 9 ofall of the core elements 5, 6 lie in a common plane.

A first and a second connecting part 11, 12 are mounted pivotably on theupper support part 7. The pivot axes 13, 14 lie parallel to thelongitudinal extent of the mattress (i.e. parallel to the viewingdirection A). The connecting parts 11, 12 can be of rod-shaped orplate-shaped design (with width extents in the direction of thelongitudinal extent of the mattress).

At their lower ends, the connecting parts 11, 12 have rollers 15, 16with which they rest on a respective supporting surface 17, 18.

Instead of rollers, sliding parts with which the connecting parts 11, 12rest on the supporting surfaces 17, 18, which then form slidingsurfaces, would basically also be conceivable and possible, but lesspreferred.

In the exemplary embodiment, the supporting surfaces 17, 18 are formedby separate supporting parts 9 b, 9 c which are attached to aplate-shaped base part 9 a of the lower supporting part 9.

It would also be conceivable and possible for separate supporting partsto be dispensed with and for the supporting surfaces 17, 18 to be formeddirectly by the surface of the base part 9 a that faces the uppersupport part 7.

The connecting parts 11, 12 are positioned obliquely, i.e. are inclinedin relation to the vertical, specifically in opposite directions. Theconnecting parts 11, 12 have the smallest inclinations in the unloadedstate of the mattress, in which the upper and lower support part 7, 9are at the greatest possible distance from each other. When the uppersupport part 7 is compressed in the direction of the lower support part9, the inclination of the connecting parts 11, 12 is increased bypivoting about their respective pivot axes 13, 14 and by the respectiverollers 15, 16 rolling along the respective supporting surfaces 17, 18.

In the unloaded state of the mattress, the connecting parts 11, 12 arepreferably inclined in relation to the vertical by a respective angle19, 20 lying within the range of between 10° and 40°.

In the unloaded state of the mattress, the lower ends of the connectingparts 11, 12, i.e. the rollers 15, 16 in the exemplary embodiment, reston the stops 21, 22 which delimit the supporting surfaces 17, 18. Theconnecting parts 11, 12 are pulled at their lower ends against the stops21, 22 by springs 23, 24.

The springs 23, 24 are therefore connected at one of their ends to therespective connecting part 11, 12 (at a distance from the respectivepivot axis 13, 14) and at their other end to an adjustment element 25,for example, as illustrated, to an adjustment element 25 common to bothof the connecting parts 11, 12 via traction cables 27, 28.

In the exemplary embodiment, the adjustment element is an electricmotor, in particular stepper motor. A cable drum 26 can be rotated bysaid electric motor in order to wind the traction cables 27, 28 to agreater or lesser extent onto the cable drum 26 or to unwind themtherefrom.

In order to clarify the different pretensioning of the springs 23, 24, amore greatly pretensioned state of the springs 23, 24 is indicated inFIG. 3 above the springs 23, 24 by dotted lines.

For the sake of simplicity, a control system for activating themotorized adjustment element 25 is not illustrated in FIGS. 3 and 4. Theactivation of the adjustment element 25 can take place in a wired orwireless manner.

However, the activation of the adjustment element 25 can also take placefully automatically by the use of sensors.

The stops 21, 22 are located at the mutually facing ends of thesupporting surfaces 17, 18. At the mutually averted ends of thesupporting surfaces 17, 18 there are further stops 31, 32 which limitthe maximum oblique position of the connecting parts 11, 12 andtherefore the maximum compressing of the upper support part 7 in thedirection of the lower support part 9.

In the exemplary embodiment, the two connecting parts 11, 12 areinclined in opposite directions in such a manner that their upper endslie more closely together than their lower ends. However, oppositelydirected inclinations the other way around, such that their upper endstherefore lie further apart than their lower ends (also see FIG. 5) arelikewise possible.

In the region of the two side edges of the core elements 6, 8,compression springs 29, 30 are furthermore arranged between the upperand the lower support parts 7, 8. Additional stability of thearrangement, for example against lateral tilting, is achieved by saidcompression springs. However, the spring constants of the compressionsprings 29, 30 are relatively soft in order not to substantially impairthe possibilities of adjusting the core element 6.

In addition to adjustable core elements 6 the mattress core 1 in theexemplary embodiment, as already mentioned, also has non-adjustable coreelements 5. For example, the latter can be designed in such a mannerthat they have an upper and a lower plate-shaped support part andcompression springs arranged in between.

According to FIGS. 1 and 2, the non-adjustable core elements 5 havegreater widths than the adjustable core elements 6. Instead, thenon-adjustable core elements 5 could also have the same widths orsmaller widths than the adjustable core elements 6.

According to FIGS. 1 and 2, the adjustable core elements 6 all have thesame width; likewise the non-adjustable core elements 5 also all havethe same width. Instead, the adjustable core elements 6 and/or thenon-adjustable core elements 5 could also have different widths.

The stops 21, 22 could also be dispensed with and the maximum distancebetween the upper support part 7 and lower support part 9 could belimited in another manner, for example by cords connecting the uppersupport part 7 to the lower support part 9.

The adjustment element 25 designed in particular as an electric motorcould also be arranged on the upper support part 7.

If the mattress is arranged in the reverse position in comparison toFIG. 3, the upper support part 7 therefore becomes the lower supportpart and the lower support part 9 becomes the upper support part. Theconnecting parts 11, 12 are then mounted pivotably at their free ends onthe lower support part and are supported at their upper ends on asupporting surface 17, 18, along which the upper end is mounteddisplaceably in a sliding or rolling manner.

In the further exemplary embodiments described below, such swapping of“bottom” and “top” is also conceivable and possible.

A second exemplary embodiment of an adjustable core element isillustrated in FIG. 5. Apart from the differences described below, thedesign corresponds to that of the first exemplary embodiment and thedescription for the first exemplary embodiment is usable analogously tothis extent.

In this exemplary embodiment, the oppositely directed inclination of thetwo connecting parts 11, 12 is realized in such a manner that theirupper ends are further away from each other than their lower ends. In acorresponding manner, the stops 21, 22 are located at the mutuallyaverted ends of the supporting surfaces 17, 18. The supporting surfacesare formed here by the surface of an individual supporting part 9 b thatfaces the upper support part 7. A stop piece 9 b which forms the stops31, 32 for limiting the maximum inclination of the connecting parts 11,12 is located in the central region.

However, the inclination of the connecting parts 11, 12 could also bedesigned in a manner corresponding to that of the first exemplaryembodiment.

The lower ends of the connecting parts 11, 12 are pulled in turn againstthe stops 21, 22 by the springs 23, 24. The other ends of the springsare in turn connected to an adjustment element 25. The latter is formedhere by an electric cylinder (=electric lifting cylinder). A yoke 34 towhich the end of the spring 24 is directly fastened is attached to thelifting rod of said electric cylinder. The other spring 23 is connectedat its end remote from the connecting part 11 to the yoke 34 via atraction cable 27 which is guided via a deflecting pulley 35 (ordeflecting drum).

Adjustment of the electric cylinder enables the pretensioning of thesprings 23, 24 to be adjusted, as a result of which the hardness of thecore element 6 can be adjusted.

A third exemplary embodiment of an adjustable core element isillustrated in FIG. 6. Apart from the differences described below, thedesign corresponds to that of the first exemplary embodiment and thedescription for the first exemplary embodiment is usable analogously tothis extent.

In this exemplary embodiment, those ends of the springs 23, 24 which areremote from the connecting parts 11, 12 are connected via a tractioncable 27 which acts on the two springs 23, 24 and is guided viadeflecting pulleys 36, 37. An electric cylinder is arranged as anadjustment element 25 between the deflecting pulleys, the lifting rod ofwhich electric cylinder is adjustable at right angles to the rectilinearconnection between the two springs 23, 24 and the traction cable 27 isguided via the end of said lifting rod. Adjustment of the electriccylinder makes it possible in turn for the pretensioning of the springs23, 24 to be changed.

A fourth exemplary embodiment of an adjustable core element isillustrated in FIG. 7. Apart from the differences described below, thedesign corresponds to that of the first exemplary embodiment and thedescription for the first exemplary embodiment is usable analogously tothis extent.

In the fourth exemplary embodiment, an electric motor is again providedas the adjustment element 25, but said electric motor acts here on thesprings 23, 24 via a helical gearing (=spindle lifting gearing). Thespindle 38 which is driven by the electric motor has a portion 38 ahaving a right-hand thread and a portion 38 b having a left-hand thread.Nuts 39, 40 are arranged on the threaded portions of the spindle, saidnuts being secured against rotation, for example by having a borethrough which a guide bar 41 passes. Those ends of the springs 23, 24which are remote from the connecting parts 11, 12 are attached to thenuts 39, 40.

Rotation of the spindle with the adjustment element 25 enables thepretensioning of the springs 23, 24 to be changed.

In this exemplary embodiment, a handwheel can be provided in a simplemanner as the adjustment element 25 instead of the electric motor, foradjusting the hardness of the core element 6 manually.

A fifth exemplary embodiment of an adjustable core element isillustrated in FIGS. 8 and 9. Apart from the differences describedbelow, the design corresponds to that of the first exemplary embodimentand the description for the first exemplary embodiment is usableanalogously to this extent.

In this exemplary embodiment, the two connecting parts 11, 12 run in acrossed manner, as seen in the view of FIG. 8, but at the mutualdistance from each other, cf. FIG. 9.

The lower support part 9 is formed integrally here (only by the basepart 9 a of the preceding exemplary embodiments) and the inner surfaceof the lower support part 9 here directly forms the supporting surfaces17, 18 for the connecting parts 11, 12.

In the unloaded state of the core element 6, the rollers 15, 16 arepulled against the stops 21, 22 by an individual spring 23. For thispurpose, a traction cable 27 is attached to the first connecting part 11and runs over a deflecting drum 42 (or deflecting pulley) which isattached to the other connecting part 12. The other end of the tractioncable 27 is connected to the one end of the spring 23, the other end ofwhich is connected to the adjustment element 25 which, for example, isagain formed by an electric cylinder.

A sixth exemplary embodiment of an adjustable core element isillustrated in FIG. 10. Apart from the differences described below, thedesign corresponds to that of the first exemplary embodiment and thedescription for the first exemplary embodiment is usable analogously tothis extent.

In this exemplary embodiment of the invention, the connecting parts 11,12 are dispensed with. Instead, a support part 43 is arranged at adistance from the lower support part 9, wherein the distance of thesupport part 43 from the lower support part 9 can be changed asdescribed below.

The springs 23, 24 interacting with the connecting parts 11, 12 in thepreviously described exemplary embodiments are likewise dispensed with.Instead, the compression springs 29, 30, which are configured with asuitable hardness, are supported at one end on the upper support part 7and at the other end on the support part 43.

The maximum distance between the upper and the lower support parts 7, 9is limited by connecting element, for example cords 44, 45 (or, forexample, telescopic elements) running between the upper and the lowersupport parts 7, 9.

An increase or reduction in the distance between the support part 43 andthe lower support part 9 causes an increase or decrease in thepretensioning of the compression springs 29, 30.

In order to change the distance between the support part 43 and thelower support part 9, use is made here of wedge elements 46, 47 whichare arranged on the lower side of the support part 43 and interact withtransversely displaceable mating wedge elements 48, 49. The transversedisplacement of the mating wedge elements can take place, for example asillustrated, by the use of a helical gearing, wherein a spindle which isconnected to the mating wedge elements 48, 49 is adjustable in thetransverse direction by rotation of same in relation to a fixed nut 50.The spindle can be rotated, for example, by manual rotation of anadjustment element 25 designed in the form of a handwheel. A motorizeddrive could also be provided.

Instead, the rotatable spindle could be fixed in the transversedirection and the nut which is connected to the mating wedge elementscould be adjusted by rotation of the spindle.

Instead of a helical gearing, it would also be possible, for example,for an electric cylinder to be used as the adjustment element.

The invention provides a reasonably priced, effective and uncomplicatedpossibility of setting the rigidity of a mattress or a mattress core.The functionality is ensured over a long period of time with differentsettings and loadings.

Key to the Reference Numbers:  1 Mattress core  2 Cushioning layer  3Cushioning layer  4 Mattress cover  5 Core element, non-adjustable  6Core element, adjustable  7 Upper support part  8 Upper support surface 9 Lower support part  9a Base part  9b Supporting part  9c Supportingpart  9d Stop piece 10 Lower support surface 11 First connecting part 12Second connecting part 13 Pivot axis 14 Pivot axis 15 Roller 16 Roller17 Supporting surface 18 Supporting surface 19 Angle 20 Angle 21 Stop 22Stop 23 Spring 24 Spring 25 Adjustment element 26 Cable drum 27 Tractioncable 28 Traction cable 29 Compression spring 30 Compression spring 31Stop 32 Stop 34 Yoke 35 Deflecting pulley 36 Deflecting pulley 37Deflecting pulley 38 Spindle 38a Portion 38b Portion 39 Nut 40 Nut 41Guide bar 42 Deflecting drum 43 Support part 44 Cord 45 Cord 46 Wedgeelement 47 Wedge element 48 Mating wedge element 49 Mating wedge element50 Nut

1. A mattress, comprising: a mattress core which has a plurality ofelastically compressible core elements at least some of the elasticallycompressible core elements are adjustable in their hardness, the coreelements which are adjustable in their hardness have an upper supportpart with an upper support surface, a lower support part with a lowersupport surface and at least one pretensioned spring, wherein the atleast one pretensioned spring generates a pretensioning force by whichthe upper and lower support parts are held at a mutual distance, and thepretensioning force of the at least one pretensioned spring isadjustable.
 2. The mattress as claimed in claim 1, further comprising atleast one device that limits a maximum distance between the uppersupport part and the lower support part.
 3. The mattress as claimed inclaim 1, further comprising at least one oblique rod- or plate-shapedconnecting part which, at an upper end thereof, is mounted pivotably onthe upper support part and, at a lower end thereof, is supported on asupporting surface, on which the lower end is mounted displaceably in asliding or rolling manner, or which, at the lower end, is mountedpivotably on the lower support part and, at the upper end, is supportedon a supporting surface, along which the upper end is mounteddisplaceably in a sliding or rolling manner, and the spring acts on theconnecting part or on a part connected thereto.
 4. The mattress asclaimed in claim 3, wherein in an unloaded state of the mattress, thespring pulls the connecting part against a stop delimiting thesupporting surface.
 5. The mattress as claimed in claim 4, wherein inthe unloaded state, the connecting part encloses an angle within a rangeof between 10° and 40° with vertical.
 6. The mattress as claimed inclaim 3, wherein the at least one oblique rod- or plate-shapedconnecting part comprises first and second rod- or plate-shapedconnecting parts which are inclined in opposite directions and are actedupon by the at least one pretensioned spring and which are each mountedpivotably at the upper ends thereof on the upper support part and aresupported at the lower ends thereof on a respective supporting surface,on which the respective lower end is mounted displaceably in a slidingor rolling manner, or which are each mounted pivotably at the lower endsthereof on the lower support part and are supported at the upper endsthereof on a respective supporting surface, along which the respectiveupper end is mounted displaceably in a sliding or rolling manner.
 7. Themattress as claimed in claim 1, further comprising a motorizedadjustment element for adjusting the pretensioning of the at least onespring.
 8. The mattress as claimed in claim 7 wherein, the adjustmentelement comprises an electric motor or an electric cylinder which isconnected to one end of the at least one spring.
 9. The mattress asclaimed in claim 7, further comprising a manually actuable adjustmentelement for adjusting the pretensioning of the at least one spring. 10.The mattress as claimed in claim 1, wherein the upper and lower supportsurfaces of the upper and lower support parts of a respective one of theadjustable core elements extends over an entire width of the mattresscore.
 11. The mattress as claimed in claim 1, wherein the upper and thelower supporting parts are rigid.